Apparatus for the drilling of and the protection of drill cores in deep-welldrilling operations



Sept. 21, 1965 HUGEL 3,207,240

METHOD OF AND APPARATUS FOR THE DRILLING AND OF THE PROTECTION OF DRILLGORES IN DEEP-WELL-DRILLINGS PRIOR To THE ACCESS OF THE DRILL FLUIDFiled 001.,- 31; 1961 INVENTOB HELMUT HUGEL ATTORNEY.

United States Patent 3,207,240 APPARATUS FOR THE DRILLING OF AND THEPROTECTION OF DRILL CORES IN DEEP-WELL- DRILLIVG OPERATIONS HelmutHiigel, Salvador-Bahia, Brazil, assignor to Tiefbohr-Messdienst Leutert& Hugel G.m.b.H., Luneburg- Erbstorf, Germany, a corporation of GermanyFiled Oct. 31, 1961, Ser. No. 148,912 5 Claims. (Cl. 175-44) The presentinvention relates to an apparatus for the drilling of drill cores indeep-Well drillings, and for the protection of the drill cores fromcontact with the drilling fluid during the drilling and removal of thecores from the deep-well drillings.

The removal of drill cores, not contacted by the drilling fluid fromdeep-well drillings, is often of importance for purposes of geologicalinvestigations of the nature of the rock and/ or the materials whichconstitute the drill cores. It is desirable, for economic reasons, todrill the longest possible cores within the shortest possible time,whereby the rate of core recovery, as related to the time expended inthe core drilling process, is as high as possible.

During the drilling of cores, in accordance with a rotary system, anannual space is drilled by means of a core drilling bit and the loosenedparticles of the materials in which the drilling is taking place flowupwardly in the drill hole alongside the drilling apparatus along withthe drilling fluid. Concurrently therewith, the core being drilledpenetrates into a core tube, which is preferably secured againstrotation relative to the core which is, at this point, still connectedat its lower extremity to the ground in which the drilling is takingplace. The provision of a non-rotatable core tube within which the coremay pentrate, prevents grinding of the core and attendant damagethereto.

In many cases, a core protecting liquid is provided in the core tube toprotect the core from contact with the drilling fluid, whereby itbecomes necessary that the core displaces the protecting liquid upon theentry of the core into the core tube. In many core drilling apparatuswhich utilize a rotatable core tube, the liquid displaced by the entryof the core into the core tube is flowed through a one-way valve intothe rising stream of drilling fluid in the space outside of the drillpipe; while in other core drilling apparatus, particularly those whichuse nonrotatable core tubes, the flow of the liquid is likewisedisplaced through a one-way valve into the space inside of the drillpipe through which the drilling fluid circulates. If an attempt is madeto remove the protective liquid displaced by the core, in core drillingapparatus which utilize a stationary core tube, from the space inside ofthe drill pipe to the space outside of the drill pipe, sealing andfrictional difliculties are encountered in the bearing assembly whichprovides for rotation of the drill pipe relative to the non-rotatablecore tube. Since high pressure prevails in the space inside of therotatable drill pipe in which the drilling fluid flows, and into whichthe one-way valve opens, relative to the pressure in the space in thedrill hole out-side of the drill pipe, this high pressure being causedby the relatively restricted discharge nozzles in the drill bit, thecore of material which penetrates into the core tube is subjected tothis high pressure, whereby an appreciable load is placed on the upperextremity or head of the core, particularly in the case of cores ofdesirably large cross-sectional area. This appreciable load has thetendency to substantially damage the core, especially in cases, whereinthe core is constituted of relatively soft, or cracked, rock material,and in any event makes more difficult, or even 3,207,240 Patented Sept.21, 1965 impossible, the penetration of the core into the core tube dueto the wedging of the core in the core tube. A further disadvantageinherent in the use of one-way valves for the protective fluid displacedfrom the core tube by the penetration of the core thereinto resides inthe fact that the one-way valve may lose its sealing properties due tothe possibility that loose material may accumulate on the valve seat toprevent proper seating of the valve thereon. In this instance, thedrilling fluid stream then has access to the core due to the inoperativecondition of the one-way valve, whereby the drilling fluid can wash outa substantial portion, or all of the core from the core tube during theflow of the drilling fluid thereto. In addition, the weight of thedrilling fluid accumulated in the core tube above the core due to thefailure of the one-way valve can function to press the core downwardlyand out of the core tube, resulting in a loss of the core during theraising of the drill pipe upon the termination of the core drillingprocess.

It is, therefore, one object of the present invention to provide anapparatus for the drilling and protection of drill cores in deep-welldrillings which avoids the significant disadvantages of the coredrilling apparatus used herebefore.

It is another object of the present invention to provide an apparatusfor the drilling and protection of drill cores in deep-well drillings,prior to further drilling therein, wherein, particularly in connectionwith core drills utilizing non-rotating core tubes, fluid pressure onthe upper extremity or head of the core is relieved to the extent thatonly the hydrostatic fluid pressure prevailing at the bottom of thedrill hole due to the weight of the drilling fluid outside of the drillpipe is to be overcome. Thus, the danger of the fluid pressure pressingthe core downwardly and out of the core tube upon termination of thecoring operation is substantially eliminated, whereby the core catchingmeans need only function to tear the core from the well upon terminationof the core drilling apparatus, and to support the weight of the coreduring the raising of the drill pipe for retrieval of the core.

It is still another object of the present invention to provide a coredrilling apparatus for the drilling and pro tection of drill cores indeep-well drillings, wherein contact of the drilling fluid with the coreduring the drilling of the core, and the penetration of the drillingfluid into the core tube is substantially inhibited to preventcontamination of the core by the drilling fluid. This preventspenetration of the drilling fluid into porous cores, as for examplecores of oil saturated sand, which penetration would, of course, resultin contaminated connate water conditions and seriously impair theaccuracy of the geological investigations of the core material.

The objects of the present invention are achieved by the use of coredrilling apparatus which comprises a nonrotatable protection tubesupported within a rotatable drill pipe from suitable bearing meanspositioned therebetween. A core tube, which is preferably split alongthe longitudinal axis thereof to provide for the convient removal ofreadily breakable cores therefrom, is supported within the saidprotection tube. The protection tube is tightly closed at its upper end,as for example by suitable plug means, and the annular space between theprotection tube and the core tube is connected with an annular channelprovided in a non-rotatable core-catching housing which may includemarking knife means as in the case of core drilling apparatus which isused for raising oriented drill cores. The annular channel is disposedin the drill bit as close as possible above the core cutting edges ofthe drill bit, and lateral openings extend outwardly from the annularchannel through the drill bit through the exterior thereof. The annularchannel is sealed by means of an O-ring having a low coeflicient offriction with relation to steel, as for example Teflon, relative to thespace between the drill bit and the core-catching housing in which thedrilling fluid circulates, whereby easy rotation of the drill bit ispossible about the non-rotating core-catching means during the coredrilling operation. The protective liquid within the core tube displacedby the penetration of the core thereinto will, in this arrangement, flowfrom the interior of the core tube into the space between the core tubeand the protection tube and downwardly therefrom for flow from the coredrilling apparatus through the above-mentioned channels in thecorecatching housing and the outwardly extending lateral opening in thedrill bit. The protective liquid will thus flow from the core drillingapparatus into the space between the drill pipe and the walls of thedrill hole against the relatively low hydrostatic pressure prevailingtherein due to the weight of the drilling fluid in the drill hole, andthe friction between the drilling fluid and the opposed surfaces of thedrill pipe and the drill hole wall.

In the use of a protective liquid to obtain a core which has not beensubjected to contact with the drilling fluid, which is desirable, forexample, in the drilling of cores in oil-bearing sand, the core tube andthe space between the core tube and the protection tube can be filledwith the protective liquid prior to the assembly of the core drillingapparatus. The said protective liquid may, for example, take the form ofa paraflin or wax mixture which melts at a temperature to be expected atthe bottom of the drill hole. Alternatively, the protective liquid maytake the form of a suitable plastic material, which is introduced intothe core tube in its liquid state and then polymerizes and solidifiesafter the expiration of a predetermined time period, or upon beingraised to a predetermined temperature. To this end, a hollow, cup-shapedprotection plug, secured at the lower extremity of the core catchinghousing through the use of a shear pin, is sealed by means of an annularO-ring, in order to retain the paraffin or liquid plastic material inthe core tube until it is displaced by the protection plug upon theshearing of the shear pin and upward movement of the protection pluginto the core-catching housing and core tube due to entry of the corethereinto.

The outwardly extending lateral openings in the drill bit which providefor the flow of the protective liquid displaced by the entry of the coreinto the core-catching housing and core tube, as described above, may beplugged prior to the introduction of the protective fluid into the coretube by suitably yieldable plugs of any readily drillable material, asfor example soft lead. The said protection plug is provided with aspring controlled check valve disposed in the bottom wall of theprotection plug and permitting flow only into the core tube. The checkvalve functions as a pressure compensator for equalizing the pressure inthe protective liquid inside the core tube with the pressure in thedrill hole. Since the protective liquid is initially at atmosphericpressure, and the pressure in the drill hole as the core drillingapparatus is lowered thereinto becomes greater than atmospheric, aslight compression of the protective liquid may occur as the coredrilling is lowered into the drill hole. Without provision for pressurecompensation between the drill hole and the interior of the core tube,the higher pressure Within the drill hole acting on the exterior of theprotection plug might very probably cause premature shearing of theshear pin which secures the protection plug to the corecatching housing.As the core penetrates into the core tube, it pushes the protection plugahead of it, whereby the protection plug functions as the piston toexpel the protective liquid from the core tube. A coating of theprotective liquid will, however, remain on the inner wall of the coretube to contact and protect the surfaces of the core as the latterpenetrates into the core tube. The drill bit is equipped with a corecutting ring which is adapted to protect the core during the cutting ofthe latter, with the cutting ring having an inner diameter whichcorresponds to the outer diameter of the core cut thereby. The loweredge of the core cutting ring may be disposed in the same horizontalplane as the lower edge of the drill bit. Alternatively, the lower edgeof the cutting ring can be disposed below the lower edge of the drillbit, if the cores are being cut from relatively soft material, as forexample soft rock, and rapid Wear of the cutting edges of the corecutting ring is not to be expected. The cutting edges of the corecutting ring and the drill bit are preferably equipped in a conventionalmanner, with hard metal or diamond faces.

Upon the removal of the core drilling apparatus from the drill hole, theprotective liquid remaining in the core tube which surrounds the corenow penetrated thereinto, will not flow from the core tube, since thedensity of the protective liquid is lower than the density of thedrilling fluid which surrounds the drill pipe in the drill hole.Preferably, the protective liquid solidifies prior to the final removalof the core drilling apparatus from the bore hole to thus form a solid,protective coating around the core. It is not, however, necessary thatthe protective liquid solidify around the core under all circumstances.

With these and other objects in view, which will become apparent in thefollowing detailed description, the present invention will be clearlyunderstood in connection with the accompanying drawings, in which:

FIGURE 1 is an axial section of core drilling apparatus constructed inaccordance with a presently preferred embodiment of the presentinvention; and

FIG. 2 is a horizontal section taken along the lines 2-2 of FIG. 1.

Referring now to the drawings, the depicted core drilling apparatuscomprises a non-rotating protection tube 1, closed at its upper end by aplug 1. A core tube 2 is positioned as shown within the protection tube1, and is preferably split longitudinally as indicated at 2 tofacilitate the removal therefrom of readily breakable cores, asdiscussed above. A rotatable drill pipe 4 surrounds the protection tube,and the drill pipe 4 includes a bearing 3 supported in the interiorthereof by a bearing support assembly 3' extending therebetween. Theplug 1 at the upper end of the protection tube 1 includes an extension 1and a stub shaft 1 projecting therefrom for positioning of the stubshaft 1 Within the bearing 3. The stub shaft 1 includes an enlarged endportion 1 which cooperates as shown with the bearing 3 to provide forthe support of the protection tube within the drill pipe 4, and for therotation of the latter relative to the protection tube 1. Acore-catching and marking knife housing 5 is supported as shown withinthe drill pipe 4 by the attachment of the housing 5 to the protectiontube 1 in any convenient manner, as for example the threaded connectionindicated at 5'. A core drilling bit 8 is threadably attached to thelower extremity of the drill pipe 4 by an attachment member 8' so as tobe rotatable with the drill pipe 4.

The core-catching and marking knife housing 5 is provided with aplurality of axially extending bores 6 which are in fluid-flowcommunication with an annular channel 7 formed between adjacent surfacesof the housing 5 and the drilling bit 8. The bores 6 are also influid-flow communication, as made clear at 6 in FIG. 1, with the axiallyextending, annular space 6 between the interior wall of the protectiontube 1 and the exterior wall of the core tube 2.

The core-catching and marking knife housing 5 includes a plurality ofmarking knives 18 slidably mounted in axially extending grooves 19formed in the housing 5 and spring-biased radially inward by springs 20.A hollow, generally cylindrical protection plug 12, having an end Wall12' extending across one extremity thereof and being open at the otherextremity thereof, is slidably positioned as shown in an axiallyextending, core rea i ceiving bore in the core-catching and markingknife housing 5, with the marking knives 18 projecting into grooves inthe protection plug 12 in the manner made clear in FIG. 2. Theprotection plug 12 includes vertical edges 12 attached to the end wall12', which are pressed into the bottom of the drill hole at the start ofthe drilling process. The function of the marking knives 18 isthreefold; they prevent rotation of the protection tube 1 with therotating drill pipe 4 and drill bit 8 due to the contact of the knives18 with the grooves in the protection plug 12. They provide the corewith longitudinal marks for orientation purposes in cases where coreorientation is desired, as described in my co-pending application forUS. Patent, S.-N. 148,897 filed concurrently herewith, and US. PatentsNos. 2,489,566 and 2,628,816, respectively; and function ascore-catchers due to the penetration of the upper points of the knives18 into the core, when the core has penetrated into the core tube 2, ina manner described hereinbelow, and the core drilling apparatus is beingremoved from the bore hole. An abutment ring 21, longitudinally split inthe manner of the core tube 2, is point-welded to the lower extremity ofthe core tube 2. The abutment ring 21 fits in part within a groove (notshown) in the core-catching and marking knife housing 5, to thus retainthe core tube 2 stationary relative to the core-catching and markingknife housing 5.

A plurality of radially disposed bores 6' extend as shown through thedrilling bit 8 from annular channel 22 to the exterior of the coredrilling apparatus. The corecatching and marking knife housing 5 isprovided with a wear ring positioned around the lower extremitiesthereof. The wear ring includes an O-ring seal 23 mounted thereon forsealing cooperation with the adjacent rotating surface of the rotatingdrill bit 8. A drilling fluid passage 28 is formed by the axiallyextending, annular space between the interior wall of the drill pipe 4and the exterior wall of the protection tube 1, and is in fluidflowcommunication with drilling fluid passages 28' formed by the axiallyextending, annular spaces between the interior wall of the drill bit 8and the exterior wall of the core-catching and marking housing 5. Thelatter of these drilling fluid passages terminates, as shown, in fluiddischarge nozzles 9, which are formed in the drilling bit 8 and providefor the flow of the drilling fluid from the drilling bit 8 withattendant rotation thereof. Thus, it may be understood whereby the sealring 23 enables rotation of the drilling bit 8 relative to thenon-rotating core-catching and marking knife housing 5, while preventingthe introduction of the relatively high pressure drilling fluid into theannular channel 22, from where it could conceivably flow into contactwith the interior of the core tube 2 through axial bores 6 and theaxially extending, cylindrical space 6 between the core tube 2 and theprotection tube 1.

The drilling bit 8 is provided with cutting edges 26 for the drilling ofthe drill hole during the core drilling operation, and a core cuttingring 13 is attached to the lower extremity of the drilling bit 8 in anyconvenient manner, as for example by welding, to cut the core uponrotation of the drilling bit 8. The fluid discharge nozzles 9 and corecutting ring 13 are relatively positioned in and on the drilling bit 8,so that the drilling fluid discharged from the nozzles 9 will contact,and cool, the outer, cylindrical wall of the cutting ring 13 to cool it,and the .core being cut thereby, to prevent heating of the core andattendant, serious damage thereto. At the same time, however, thevertical extent of the cutting ring 13 will prevent the direct flow ofthe drilling fluid from the discharge nozzles 9 into contact with thecore being cut.

The protection plug 12 is initially connected to the corecatching andmarking knife housing 5 by means of a shear pin 11 extendingtherebetween. The protection plug 12 includes an O-ring 33 positionedthereon, and the O-ring 6 33 cooperates initially with the interior wallof the cutting ring 13, and then with the interior wall of the portion21 of the drilling bit 8, the wall of the axially extending bore in thecore-catching and marking knife housing 5, and the interior wall of thecore tube 2 respectively, to seal the interior of the core tube 2 fromthe drilling fluid Within the drill hole as the core forces theprotection plug 12 into the core tube 2 in the manner described indetail hereinbelow. A filling plug 35 is provided in the end wall 12' ofthe protection plug 12 and functions to enable the air-free filling ofthe interior of the protection plug 12 and of the core tube 2 with theparaffin, wax, or liquid plastic, protective liquid described above. Acheck valve 14 also extends as shown through the end wall 12 of theprotection plug 12 and provides for limited flow of drilling fluid fromthe bore hole into the interior of the protection plug 12 for pressurecompensation purposes in the manner described above.

Yieldable plug means 6 and 9 of any readily drillable material, as forexample a lead alloy or plastic, are provided as shown in the radiallyextending bore 6' and the fluid discharge nozzles 9, respectively, whichare formed in the drilling bit 8. The plug means 6 and 9 are eachdesigned to yield upon the application of a predetermined pressurethereto, and function, in the case of plug means 6 to retain theprotective fluid within the core drilling apparatus until a corecommences the penetration thereinto, and in the case of plug means 9, toprevent the entry of cuttings from previous drilling into the fluiddischarge nozzles 9 as the core drilling apparatus is lowered to thebottom of the drill hole. Once the core drilling apparatus has beenlowered to the bottom of the drill hole, and the core cutting operationcommenced by the introduction of the highly pressurized drilling fluidto the drill pipe 4, the plug means 6 and 9 are readily forced from thedepicted positions thereof into the drill hole by the respectivepressures of the protective liquid, and drilling fluid.

In operation, with the core drilling apparatus of the present inventionfilled with the protective liquid, and the plug means 6 and 9 positionedtherein in the depicted manner, the apparatus is lowered to the bottomof the drill hole and the highly pressurized drilling fluid introducedthereto through the drill pipe 4. As the plug means 9 are forced fromthe fluid discharge nozzles 9 by the highly pressurized drilling fluid,and the drilling bit 8 commences to rotate, the core cutting ring 13will cut the core as indicated at 15 in FIG. 1. As the core is cut, itwill force the protection plug 12 upwardly in the axially extending borein the core-catching and marking knife housing 5 toward the core tube 2,due to the weight of the apparatus acting on the housing 5 and the coretube 2. As the protection plug 12 starts rising within the core-catchingand marking knife housing 5, pressure will be exerted on the protectiveliquid within the interior of the protection plug 12 and of the coretube 2. This pressure will be communicated through the protective liquidto the plug means 6 in the radially extending bores 6, whereby the plugmeans 6 will be forced out of the radially extending bores 6' and theprotective liquid will commence to flow from the interior of the coretube 2, over the top of the core tube 2 or through its axial slots,through the axially extending, cylindrical space 6 the axially extendingbores 6 in the core-catching and marking knife housing 5, the annularchannel 7, and the radially extending bores 6', respectively, to theexterior of the drilling bit 8. As the protective liquid leaves thedrilling bit 8, it will be carried upwardly by the drilling fluid,

. which is jetted through nozzles 9 and rises in the drill channelsystem described above down to the radial bores 6 in the core bitcontain protective liquid, except for the space occupied by the volumeof the core rising into the core tube 2, such liquid being alwayspresent around the core shown to the lower edge of the marking knifehousing and by downwardly directed displacement of the protective fluideven within the core bit, no drilling fluid having access to this space,as explained above. The protective fluid thus completely covers the coreas the latter penetrates into the core bit and eventually into the coretube 2.

During the drilling of the core, only the hydrostatic pressure due tothe weight of the drilling fluid at the bottom of the drill hole, andthe pressure due to the relatively low weight of the protection plug 12acts upon the top of the core as it penetrates into the core tube 2,whereby the core drilling operation is significantly simplified,particularly in the drilling of the cores in soft, split, or fracturedrock formations. During the removal of the core drilling apparatus fromthe bore hole upon the termination of the core drilling operation, thecore-catching and marking knife housing 5 need only function, throughthe points on the marking knives 18, to tear the drill core from theground providing it is not preferred to burn off the core by a shortadditional period of dry drilling-and to prevent the sliding of the corefrom the core tube 2 by its own weight. Thus may be understood wherebyany hydraulic load on the core head, as for example those due to thehighly pressurized drilling fluid within the core drilling apparatus,are completely eliminated by the closure of the top of the protectiontube 1 by the plug 1, and the provision of a sealing ring 23 in thewear-ring on the core catching and marking knife housing 5, and thesealing ring 33 on the protection plug 12.

While I have disclosed one embodiment of the present invention, it is tobe understood that this embodiment is given by example only and not in alimiting sense, the scope of the present invention being determined bythe objects and the claims.

I claim:

1. A core drilling apparatus for the drilling and recovery of cores fromdeep well drillings,

a rotatable drill tube,

a protection tube non-rotatably disposed within said drill tube andspaced therefrom at least in part to provide a first axially extendingspace,

an axially divided core tube disposed in said protection tube and spacedtherefrom at least in part to provide a second axially extending space,the upper end of said core tube terminating freely in said protectiontube,

means for filling the interior of said core tube with an air-free coreprotecting liquid,

means for sealing the upper end of said protection tube,

a drill bit connected to said drill tube for rotation therewith andhaving an axially extending bore formed therein,

cutting means formed on said drill bit,

a core-catching housing releasably connected to the lower end of saidprotection tube in fixed angular relationship therewith and extendinginto said axially extending bore in said drill bit in spacedrelationship therewith at least in part to provide a third axiallyextending space in fluid flow communication with said first axiallyextending space,

sealing means positioned between said core-catching housing and saiddrill bit below said third axially extending space to provide asubstantially fluid-tight seal therebetween, while enabling freerotation of said drill bit relative to said core-catching housing,

annular channel means formed between said core-catching housing and saiddrill bit below said sealing means and there being means preventingfluid communication between said annular channel means and said thirdaxially extending space,

radially extending third flow bores formed in said drill bit andextending theret-hrough above said cutting means in fluid flowcommunication with both said annular channel means and the exterior ofsaid core drilling apparatus,

means maintaining said core tube in fixed angular relation to saidcore-catching housing,

a plurality of axially extending fluid flow bores formed in saidcore-catching housing and extending therethrough in fluid flowcommunication with both said annular channel and said second axiallyextending space,

a plurality of fluid nozzles extending in said drill bit from said thirdaxially extending space to the exterior of said core drilling apparatusbelow said radially extending bores,

a core cutting ring attached to the lower end of said drill bit radiallyinwardly of said nozzles,

an axially extending, core-receiving bore in said corecatching housing,

said bore being in communication with the exterior of said core drillingapparatus and in susbtantial alignment with the interior of said coretube, and

a protection plug slidably mounted in said core-receiving bore insubstantially fluid-tight relationship therewith and movable upwardlytherefrom into the interior of said core tube upon the entry of a coreinto said core receiving bore, whereby drilling fluid may be introducedto the core drilling apparatus through said first axially extendingspace and-flow therefrom, remote from the interior of said core tube,through said third axially extending space and from said third axiallyextending space through said fluid nozzles to the exterior of the coredrilling apparatus when said drill bit is rotated to cut a core, and

said protection plug may be moved upwardly into the interior of saidcore tube upon the entry of the core into said core receiving bore todisplace said core protecting liquid from the interior of the core tubefor the flow of the core protecting liquid over said freely terminatingend of the core tube and through the axial division of the latter,respectively into said second axially extending space and therefrom tothe exterior of the core drilling apparatus above said cutting edges andnozzles, through said axially extending, fluid flow bores, said annularchannel, and said radially extending, third flow bores, respectively.

2. The core drilling apparatus, as set forth in claim 1,

wherein said protection plug comprises a hollow, generally cylindricalmember open at its upper end in fluid-flow communication with theinterior of said core tube,

an end wall extending across the lower end of said protection plug,

check valve means in said end wall permitting fluid flow only in thedirection from the exterior of the core drilling apparatus to theinterior of said core tube,

said check valve means being adapted to enable pressure equalizationbetween the drilling fluid at the exterior of the core drillingapparatus and the core protecting liquid in the interior of said coretube during the drilling of a core,

said means for filling the interior of said core tube with an air-free,core protecting liquid comprising a filling plug removably positioned insaid end wall of said protection plug.

3. The core drilling apparatus, as set forth in claim 1,

further comprising a shear pin extending between said core-catchinghousing and said protection plug to maintain the latter properlypositioned in said core receiving bore prior to the start of thedrilling of a core and to shear off as the core is drilled to'enable thesaid protection plug to move upwardly into the interior of said coretube upon the entry of a core into said core receiving bore, and

plug means yieldably positioned in said radially extending, third-flowbores and said fluid nozzles, respectively, and displaceable therefromto the exterior of the core drilling apparatus by the pressure of saidcore protecting liquid and said drilling fluid, respectively, uponcommencing the drilling of a core. 4. The core drilling apparatus, asset forth in claim 1, further comprising sealing means disposed betweensaid protection plug and said core receiving bore for preventing theentry of drilling fluid into said core receiving bore around theperiphery of said protection plug. 5. The core drilling apparatus, asset forth in claim 1, wherein said cutting means formed on said drillbit comprise drill hole cutting edges for cutting the drill hole duringthe drilling of a core, and said core cutting ring and said fluiddischarge nozzles being arranged on said drill bit such that thedrilling fluid discharged from said fluid discharge nozzles will contactand cool the core cutting ring, to in turn cool 10 the core being cut,but is prevented by said core cutting ring from flowing directly intocontact with the core being cut.

References Cited by the Examiner UNITED STATES PATENTS 1,542,172 6/24Reed et al 175-245 1,773,915 8/ 30 Lydon 17544 2,073,876 3/ 37 Oliver175-254 2,238,609 4/41 Sewell 175-245 2,313,576 3/43 Phillips et a117544 2,364,088 12/44 Miller et a1. 175-245 XR 2,643,858 6/53 Hardman175-246 2,703,697 3/55 Walker 175245 2,862,691 12/58 Cochran 1752453,064,742 11/62 Bridwell 175-246 XR FOREIGN PATENTS 296,352 8/28 GreatBritain.

CHARLES E. OCONNELL, Primary Examiner. BENJAMIN HERSH. Examiner,

1. A CORE DRILLING APPARATUS FOR THE DRILLING AND RECOVERY OF CORES FROMDEEP WELL DRILLINGS, A ROTATABLE DRILL TUBE, A PROTECTION TUBENON-ROTATABLY DISPOSED WITHIN SAID DRILL TUBE AND SPACED THEREFROM ATLEAST IN PART TO PROVIDE A FIRST AXIALLY EXTENDING SPACE, AN AXIALLYDIVIDED CORE TUBE DISPOSED IN SAID PROTECTION TUBE AND SPACED THEREFROMAT LEAST IN PAT TO PROVIDE A SECOND AXIALLY EXTENDING SPACE, THE UPPEREND OF SAID CORE TUBE TERMINATING FREELY IN SAID PROTECTION TUBE, MEANSFOR FILLING THE INTERI OF SAID CORE TUBE WITH AN AIR-FRE CORE PROTECTINGLIQUID, MEANS FOR SEALING THE UPPER END OF SAID PORTECTION TUBE, A DRILLBIT COINNECTED TO SAID DRILL TUBE FOR ROTATION THEREWITH AND HAVING ANAXIALLY EXTENDING BORE FORMED THEREIN, CUTTING MEANS FORMED ON SAIDDRILL BIT, A CORE-CATCHING HOUSING RELEASABLY CONNECTED TO THE LOWER ENDOF SAID PROTECTION TUBE IN FIXED ANGULAR RELATIONSHIP THEREWITH ANDEXTENDING INTO SAID AXIALLY EXTENDING BORE IN SAID DRILL BIT IN SPACEDRELATIONSHIP THEREWITH AT LEAST IN PART TO PROVIDE A THIRD AXIALLYEXTENDING SPACE IN FLUID FLOW COMMUNICATION WITH SAID FIRST AXIALLYEXTENDING SPACE, SEALING MEANS POSITIONED BETWEE SAID CORE-CATCHINGHOUSING AND SAID DRILL BIT BELOW SAID THIRD AXIALLY EXTENDING SPACE TOPROVIDE A SUBSTANTIALLY FLUID-TIGHT SEAL THEREBETWEEN, WHILE ENABLINGFREE ROTATION OF SAID DRILL BIT RELATIVE TO SAID CORE-CATCHING HOUSING,ANNULAR CHANNEL MEANS FORMED BETWEEN SAID CORE-CATCHING HOUSING AND SAIDDRILL BIT BELOW SAID SEALING MEANS AND THERE BEING MEANS PREVENTINGFLUID COMMUNICATION BETWEEN SAID TUBULAR CHANNEL MEANS AND SAID THIRDAXIALLY EXTENDING SPACE, RADIALLY EXTENDING THIRD FLOW BORES FORMINED INSAID DRILL BIT AND EXTENDING THIRD FLOW BORES FORMED IN SAID DRILL MEANSIN FLUID FLOW COMMUNICATION WITH BOTH SAID ANNULAR CHANNEL MEANS AND THEEXTERIOR OF SAID CORE DRILLING APPARTUS, MEANS MAINTAINING SAID CORETUBE IN FIXED ANGULAR RELATION TO SAID CORE-CATCHING HOUSING, APLURALTIY OF AXIALLY EXTENDING FLUID FLOW BORES FORMED IN SAIDCORE-CATCHING HOUSING AND EXTENDING THERETHROUGH IN FLUID FLOWCOMMUNICATION WITH BOTH SAID ANNULAR CHANNEL AND SAID SECOND AXIALLYEXTENDING SPACE, A PLURALITY OF FLUID NOZZLES EXTENDING IN SAID RILL BITFROM SAID THIRD AXIALLY EXTENDING SPACE TO THE EXTERIOR OF SAID COREDRILLING APPARATUS BELOW SAID RADIALLY EXTENDING BORES,